36 C.F.R. § 28.14
If allowable by local law and if immediate action is essential to avoid or eliminate an immediate threat to the public health or safety or a serious and immediate threat to private property or natural resources, an agency or person may commence a temporary use without a permit from the zoning authority. In all cases, the agency or person shall inform the Superintendent and send an application for a permit to the zoning authority within 10 days after the commencement of the use and the applicant shall proceed in full compliance with the provisions of the approved local zoning ordinance. When the reasons for undertaking the emergency action no longer exist, the agency or person shall cease an emergency action taken under this section.
36 C.F.R. § 28.14